The typical hard disk drive includes a head disk assembly (HDA) and a printed circuit board (PCB) attached to a disk drive base of the HDA. The head disk assembly includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The printed circuit board assembly includes electronics and firmware for controlling the rotation of the spindle motor and for controlling the position of the HSA, and for providing a data transfer channel between the disk drive and its host.
The spindle motor typically includes a rotor including one or more rotor magnets and a rotating hub on which the disk is mounted and clamped, and a stator. If more than one disk is mounted on the hub, the disks are typically separated by spacer rings that are mounted on the hub between the disks. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the rotor magnet(s), thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks.
The head stack assembly typically includes an actuator, at least one head gimbal assembly (HGA), and a flex cable assembly. During operation of the disk drive, the actuator must rotate to position the HGA adjacent desired information tracks on the disk. The actuator includes a pivot bearing cartridge to facilitate such rotational positioning. One or more actuator arms extend from the actuator body. An actuator coil is supported by the actuator body opposite the actuator arms. The actuator coil is configured to interact with one or more fixed magnets in the HDA, typically a pair, to form a voice coil motor. The printed circuit board assembly provides and controls an electrical current that passes through the actuator coil and results in a torque being applied to the actuator. A crash stop is typically provided to limit rotation of the actuator in a given direction, and a latch is typically provided to prevent rotation of the actuator when the disk dive is not in use.
Each HGA includes a head for reading and writing data from and to the disk. In magnetic recording applications, the head typically includes an air bearing slider and a magnetic transducer that comprises a writer and a read element. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer may be inductive or magnetoresistive. In optical and magneto-optical recording applications, the head may include a mirror and an objective lens for focusing laser light on to an adjacent disk surface.
An HGA includes a suspension assembly that holds the head. FIGS. 1 and 2 depict a suspension assembly 100 according to the prior art. The suspension assembly 100 includes a load beam 110 that includes a dimple 112 and may also include a loading tab 114. The suspension assembly 100 also includes a flexure 120 that includes a tongue 130 to which the head (not shown to facilitate viewing of the tongue 130) is adhered.
The flexure 120 is generally comprised of a laminate material that typically includes three layers: a structural layer 122, a dielectric layer 124, and a conductive layer 126. The conductive layer 126 includes leads that terminate near the head (e.g. terminal 138) to facilitate electrical connection. The dielectric layer 124 typically includes stand-offs (e.g. stand-off 140) on the tongue 130 to help control the spacing and maintain parallelism between a head and the tongue 130 while the head is adhered to the tongue 130. The structural layer 122 typically includes arms 134, also known as “outrigger” arms. Flexibility in arms 134 allows the tongue 130 to pivot about dimple 112 to allow pitch and roll motions of the head, although motion of the tongue 130 may be limited by a tongue limiter 136.
The dimple 112 typically comprises the same material as, and makes contact with, the structural layer 122. Often, the dimple 112 and the structural layer 122 both comprise stainless steel. The area of contact between the dimple 112 and the structural layer 122 is typically small because the dimple 112 is typically of hemispherical shape. Due to the small area of contact and the material similarity, fretting can develop at the location of dimple-flexure contact. Such fretting can lead to corrosion, which in turn can create undesirable contamination (typically iron oxide) within the disk drive. Thus, there is a need in the art for an improved flexure design that can reduce fretting and/or corrosion at the dimple-flexure contact location.